A conventional fuel injection valve is described in German Patent Application No. 36 24 476. This German Patent Application indicates that in order to improve the turbulence of the fuel in the valve needle, one or more swirl bores are provided, extending so that the bores have an axial and a tangential component with respect to a longitudinal axis of the injection valve. The fuel exiting these bores flows directly onto the valve seat face of the nozzle body. However, this conventional fuel injection valve is disadvantageous since it has a narrow opening cross section at the swirl bores, thus an unwanted force directed at the valve seat face acts on the valve needle as a result of friction, shock losses and pressure drop as the fuel flows through the swirl bores. This force (which is directed toward the valve seat face) counteracts the opening of the valve needle and can therefore cause poor valve performance.
In addition, U.S. Pat. No. 4,520,962 describes another fuel injection valve in which, instead of swirl bores, swirl grooves can be provided to improve the turbulence of the fuel because of the resulting swirl flow. With the fuel injection valve described in U.S. Pat. No. 4,520,962, however, the swirl grooves are not provided directly on the valve needle, but instead the swirl grooves are formed in a swirl element that is inserted into the nozzle body between the valve seat face and the spray orifice in the direction of flow.
German Patent Application No. 25 43 805 also describes a conventional fuel injection valve having swirl grooves on the valve needle above a feed point in the flow direction. The design of this conventional fuel injection valve includes the above-mentioned disadvantage, where an unwanted force acts on the valve needle in the closing direction due to the friction, shock losses and the pressure drop as the fuel flows through the swirl grooves, which can cause poor performance in the fuel injection valve.